Thermochromism applied to Transportation Engineering: asphalt roads and paints

Abstract

Thermochromic materials change their optical response to temperature reversibly. This study explores the application of thermochromism to road engineering, which is still incipient in this area, from two perspectives. The first one is about the development of functionalized road markings (FRM) working as thermochromic sensors to alert the presence of ice on the road and, in this way, to improve road safety. The second one concerns the functionalization of asphalt pavements for reversible color change at high temperatures to reduce energy absorption in the form of heat and, in this way, mitigate Urban Heat Islands (UHI) effect. For the development of the FRM, thermocapsules were added into acrylic ink, applied to an AC10 asphalt mixture, submitted to high and low temperatures, and visually characterized. For the functionalization aiming for UHI reduction, thermochromic solutions (TS) containing thermocapsules, dye, and resin were superficially sprayed at an AC10, and the Quick Ultraviolet Accelerated Weathering Test (QUV) was performed with subsequent Colorimetry Analysis, where the color coordinates defined by the Comissione Internationale de l' Éclairage (CIE) were measured. The results show that it is possible to functionalize road marks to work as a thermochromic sensor. Also, this property can be improved by synthesizing or using thermocapsules with TT closer to the water melting point. The results also indicate that the asphalt pavement functionalization with surface spraying of TS points out to higher luminosity results in terms of color coordinate, which is intended for the mitigation of heat energy absorption, consequently mitigating the UHI.